BOSTON — The first half of the back-to-back went just according to plan.

The Bruins built a three-goal lead after two periods in Montreal on Wednesday night. They made it a four-goal bulge on the first shift of the third period. Minutes-eaters Zdeno Chara, Johnny Boychuk, Patrice Bergeron and David Krejci could put their skates up on the bench for the third period and toast a 4-1 win in style.

The second half of the back-to-back was not so kind.

The Coyotes were rested and waiting for them at TD Garden on Thursday. Phoenix is properly motivated, sitting just one point out of a playoff spot. The Bruins didn't help themselves by putting the Coyotes — the third-ranked team on the power play — on the man-advantage five times.

Chara, Boychuk, Bergeron and Krejci had to carry heavy loads to ensure a 2-0 lead after two periods hung up. The batteries were at dangerous lows by the time the clock hit zero. With Tuukka Rask coming up large in the third period, it was enough to eke out a 2-1 win, the Bruins' seventh straight victory.

The Bruins moved a point ahead of Pittsburgh for the top spot in the Eastern Conference with 16 games remaining (the Penguins have one game in hand).

"I think there's a pretty good commitment from our guys," coach Claude Julien said. "Even tonight, you could see that maybe we were getting tired by the end of the third, but they had 10 minutes of power plays and a pretty good power play at that. We had to use a lot of those same players over and over again, and usually that's not a good sign."

Chara played 26:53 of ice time, including 6:26 shorthanded. It's the most he's played in a regulation game since Feb. 1. Boychuk, Kevan Miller, Gregory Campbell, Patrice Bergeron, Matt Bartkowski, Loui Eriksson and Chris Kelly all played at least 2:40 on the penalty kill.

The Coyotes got just four shots on their five power plays, including one on a four-minute man-advantage in the first. The Bruins have killed off 16 straight power plays after some tweaks following the Olympic break.

Energy that had been abundance when the game began was gone by the end, or at least diminished to the point where anything more than hanging on by a stick blade was possible. The Bruins scored both of their goals in the first period and racked up 12 shots. They had all of eight shots on Phoenix netminder Mike Smith in the final 40 minutes.

"(Everyone was tired) pretty much the whole third period," Rask said. "It’s just a battle. It felt like an overtime game for us there. Good thing we survived."

Rask, too, was appearing on consecutive days. The goalie stopped 35 shots in Montreal on Wednesday, including 14 in a Canadiens-owned first period. The opportunity seemed to call for backup Chad Johnson to play against his old team.

Although Rask was only called on to make 21 saves Thursday — including just two in the second period — they were high on the difficulty scale.

Rask stood tall to take away Shane Doan's breakaway early in the second. He reached out with his pad to stop Lauri Korpikoski and Brandon McMillan in the third. When the Coyotes could have raced past the Bruins like the Roadrunner, Rask didn't let them.

"That's what he makes eight million dollars for," Brad Marchand said.

Rask wasn't surprised to get the call for the second straight night. He also made back-to-back starts two weeks ago against the Capitals and Rangers, and shined in the Bruins' victory at Madison Square Garden. The only goal he allowed Friday was a Lauri Korpikoski tip-in at 8:14 of the third.

"Well, I mean, not the freshest," Rask said of his body. "But I’ve been more tired."

The Bruins knew a quick start was needed Thursday. Zdeno Chara popped in his 16th goal on a shot from the slot after a poor turnover by Phoenix defenseman and Boston native Keith Yandle. With 16 goals, Chara is second in the league among defensemen and just three off his career high.

Jarome Iginla made it 2-0 with 2:29 left in the first, deflecting a Boychuk shot for his team-high-tying 21st of the season.

From there, there wasn’t much push left — only enough to hold on.

Dan Cagen can be reached at 508-626-3848 or dcagen@wickedlocal.com. Follow him on Twitter @DanCagen.